IMHO, I would just get the front 3 and a decent receiver. Save up, get the rest.
I love my Andrew Jones Pioneer towers, but even going with the bookshelf version and a center you are going to blow your budget. Those aren't made any longer (IIRC) so getting used may be your only option.
That brings up a point. For you, I'd recommend going the used route. As long as gear is taken care of, it's going to continue to work well for years to come.